1. Field of the Invention
The present invention relates to a hybrid heating apparatus to heat potable water via “free heat”, i.e., waste heat recovered by heat recovery units (such as refrigeration units) and heat from insolation units (such as by solar collection units). A single controller directs operation of a single pump to circulate fluid between at least one heat exchanger and each of the heat recovery units and insolation units and directs operation of valves to allow the fluid to be circulated to become heated before reaching the heat exchanger, which heat exchange with the potable water heats the same.
2. State of the Art
Commercial and residential facilities and dwellings include various systems for heating potable water. In generally, they primarily rely on a conventional water heater that includes either a fossil fuel (oil or natural gas) furnace or boiler or an electric water heater, although an increasing number of such facilities and dwellings have turned to a solar water heater to satisfy their demand for heating potable water to the extent feasible. If the solar water heater cannot meet the demand for potable water heating, then the conventional water heater is operated to satisfy the demand.
A solar water heater may be operated in either a closed loop system or an open loop system to heat potable water stored in a tank. In an open loop system, potable water to be heated is pumped from the tank directly to the solar water heater and back. In a closed loop system, glycol or other kind of fluid having a lower freeze temperature than that of water is pumped to the solar water heater for heating and pumped back to a heat exchanger for heating the potable water in the tank. In climates susceptible to freezing outdoor temperatures, the closed loop system for the solar water heater is used. In climates that are not susceptible to freezing outdoor temperatures, the open loop system may be used for the solar water heater.
In the case of a dedicated solar water heater, the piping may become cold when exposed to cold outdoor temperatures overnight when there is no insolation. At the time of sunrise (or later if they do not face the morning sun), the solar collectors can start again to heat fluid through insolation, but the solar water heater would be operating under a cold start and thus will need to heat the cold fluid circulating in the piping to a higher temperature before it can attempt to satisfy a demand for heating potable water.
Installation and operating costs affect the economic feasibility of incorporating a solar water heater into an existing commercial and residential facility and dwelling to satisfy needs to heat potable water. Thus, the need to heat circulating fluid in piping from a cold start adversely affects the economics of heating potable water by insolation since the conventional water heater will need to operate that much longer until the cold start condition is overcome. Further, the cost for installation and operation of a dedicated pump (and heat exchanger in the case of a closed loop) for the solar water heater adversely affect the economics of heating potable water by insolation.
JP2004012025 proposes an efficient hybrid system that improves the relationship between respective pieces of equipment in a solar system and a cogeneration system by reducing carrier power by inverter control. The hybrid system includes a solar heat collector, a heat storage tank, a heat exchanger to supply hot water, a hot water storage tank, an auxiliary boiler, a heat exchanger for collecting waste heat, a non-utility generator, an absorption type refrigerator, a refrigerating tower, a heater exchanger for heating, a system connection board for controlling the drive of each piece of equipment and a DC power supply board. The overall efficiency of operation is improved when both a solar heat collector and a refrigerant waste heat collector are used to heat water through respective heat exchangers as a supplement to a conventional boiler. However, the economics of such a system is adversely impacted by installing and running respective pumps and using respective heat exchangers for each water heating system, i.e., solar insolation, waste heat recovery, auxiliary boiler, etc.
It would be desirable to reduce the overall installation and operating costs to heat potable water that uses “free heat” from a solar water heater and refrigerant waste heat recovery units (HRU) by integrating them rather than keeping them as separate, stand-alone water heating systems.